Door knocker
A door knocker is an item of door furniture that allows people outside a house to alert those inside to their presence. A door knocker has a part fixed to the door, and a part (usually metal) which is attached to the door by a hinge, and may be lifted and used to strike a plate fitted to the door, or the door itself, making a noise. The struck plate, if present, would be supplied and fitted with the knocker. Door knockers are often ornate, but may be no more than a simple fitting with a metal bob or ring.
A British cast iron door knocker
"Ring of Mercy" on the Dom (Cathedral) St. Maria. of Augsburg.
Angel door knocker in Harderwijk, the Netherlands
Door knocker in Venice
Door knocker in Orléans, France
Door knocker in Behnam House, Iran
ِDoor knocker in Haji Bulagi House, Iran
Door knocker in Behnam House, Iran
The door knocker of Hôtel de Gournay, Paris
A door in Fez, Morocco with two knockers. Traditionally, one was used by women and the other by men.
Door knocker depicting an Eagle warrior in Querétaro, Mexico.
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Wikipedia